Conventionally, as a method of producing carbon nanotubes, a polymer blend spinning technique is known (for example, see Patent Document 1 below). Specifically, in this method, a thermally decomposable polymer that disappears as a result of heat treatment and a carbon precursor polymer that leaves carbon after heat treatment are used as starting materials to prepare a polymer blend, and the polymer blend is stretched by melt-spinning, then the carbon precursor polymer is made infusible, and thereafter carbonized to produce carbon nanotubes. This method, by which high purity carbon nanotubes can be obtained, is far superior as a mass-production technique to currently used gas phase methods.
In the process of spinning the polymer blend according to this method a continuous melt spinning technique is generally applied in which spinning is performed by heating a spinning machine that houses a polymer blend to about 300° C. in an electric furnace, supplying argon gas or nitrogen gas to the spinning machine and discharging the molten polymer blend from the spinning machine through a nozzle of the spinning machine, and winding the fiber discharged through the nozzle around a bobbin rotated by a motor.
In the continuous melt spinning technique, however, there is a problem that phase separation of the polymer blend in the spinning machine kept at a high temperature is caused due to melting, which is attributed to the long time period of spinning, and thus the desired carbon nanotubes cannot be efficiently obtained. The above-mentioned Patent Document suggests that a spinning method in which fibers are extracted using centrifugal force may be applied, but no specific centrifugal melt spinning method is disclosed therein.
Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2003-146634